This invention relates to dispensers for dispensing pulverulent coating materials (hereinafter sometimes xe2x80x9ccoating powderxe2x80x9d or xe2x80x9cpowderxe2x80x9d) suspended in gas streams, for example, stream of air, from, for example, a fluidized powder bed. It is disclosed in the context of a rotary powder dispenser (hereinafter sometimes a xe2x80x9cpowder bellxe2x80x9d or xe2x80x9cbellxe2x80x9d). However, it is believed to have utility in other applications as well.
Systems for dispensing coating powder are known. There are, for example, the systems illustrated and described in U.S. Pat. Nos. 5,853,126 and 6,328,224 and the references cited in those patents. The powder bells illustrated and described in U.S. Pat. Nos. 5,853,126 and 6,328,224 employ electrically nonconductive sleeves or bosses provided on the back side (upstream side in the direction of powder flow) of the diffuser to determine the width of the annular powder discharge opening.
According to an aspect of the invention, a dispensing apparatus is provided for a pulverulent material entrained in a stream of a transporting gas or mixture of gases. The apparatus includes a first member and a second member. The first member includes an interior into which the stream flows and a perimetral discharge edge. The second member includes a side facing the interior and a perimetral discharge edge. A discharge opening is defined between the discharge edges of the first and second members. A dimension of the discharge opening is determined by one or more third members, each having a first end adjacent the first member and a second end adjacent the second member. The third members have non-uniform transverse sections. A transverse section of each third member between its first and second ends has a smaller area than the transverse section of each third member at one its first and second ends.
Illustratively according to this aspect of the invention, a transverse section of each third member between its first and second ends has a smaller area than the transverse section of each third member at both its first and second ends.
Further illustratively according to this aspect of the invention, one of the first member and each first end includes a first threaded opening and the other of the first member and each first end includes complementary first threads for engagement in the first threaded opening. One of the second member and each second end includes a second threaded opening and the other of the second member and each second end includes complementary second threads for engagement in the second threaded opening.
Additionally illustratively according to this aspect of the invention, the apparatus includes a rotator for rotating the assembled first, second and third members about an axis of the first member.
Illustratively according to this aspect of the invention, the apparatus includes a source of high-magnitude electrical potential for providing an electrical charge to the fluidized pulverulent material as the fluidized pulverulent material is discharged. An electrode is provided on the assembled first, second and third members. Means are provided for coupling the source of high-magnitude electrical potential to the electrode.
Further illustratively according to this aspect of the invention, the apparatus includes a device for providing a fluidized stream of the pulverulent material, and a conduit for transporting the fluidized pulverulent material from the device to the interior.
Additionally illustratively according to this aspect of the invention, the first member includes an outer portion defining an exterior of the first member and a liner defining the interior.
Illustratively according to this aspect of the invention, the assembled first, second and third members include a first feature and the electrode includes a second feature complementary to the first feature for orienting the electrode with respect to the assembled first, second and third members.
Additionally illustratively according to this aspect of the invention, one of the first member and each first end includes a first threaded opening and the other of the first member and each first end includes complementary first threads for engagement in the first threaded opening. The first end includes a radially outwardly extending feature for abutting against the first member adjacent the engaged complementary first threads and first threaded opening.
Illustratively according to this aspect of the invention, one of the second member and each second end includes a second threaded opening and the other of the second member and each second end includes complementary second threads for engagement in the second threaded opening. The second end includes a radially outwardly extending feature for abutting against the second member adjacent the engaged complementary second threads and second threaded opening.
Further illustratively according to this aspect of the invention, one of the first member and each first end includes a frustoconical feature and the other of the first member and each first end includes a complementary recess for receiving the frustoconical feature.
Additionally illustratively according to this aspect of the invention, one of the second member and each second end includes a frustoconical feature and the other of the second member and each second end includes a complementary recess for receiving the frustoconical feature.